In the CDMA mobile communication system, the same radio frequency range is co-used by many users, and a base station distinguishes many users by spreading codes. With increase in the number of users, simultaneously connected to the same base station, there result increasing interferences by the communication employing the same frequency. With increase in interferences, the communication quality with the individual users is gradually deteriorated, such that the probability becomes higher that the desired signal quality cannot be achieved. If, with the view to keeping communication quality, limitations are imposed on the quantity of interferences, the number of users that may be connected to the same base station is decreased, thus leading to a reduced capacity.
That is, in the CDMA mobile communication system, there persists a correlation between the quality of communication and the communication capacity, and hence the acceptance control for a wireless section, deciding whether or not a user's line connection request is to be accepted, that is, access acceptance control, becomes crucial.
As indices for decision, used in such acceptance control, the quantity of uplink interferences, approximating the total received power in a spread band, received by the base station, and the downlink transmission power, as the total transmission power of the base station, are used for the uplink of transmission from the mobile station to the base station and for the downlink of transmission from the base station to the mobile station, respectively. The quantity of uplink interferences and the downlink transmission power are correlated with the load to a radio jurisdiction in each of the uplink and downlink.
The line connection requests from a mobile station may be classed into a new call, produced by a call initiated or a call incoming, and a handover call, produced by handover from another radio jurisdiction. In the acceptance control, the usual practice is to accept handover call preferentially, in order to prevent the communication line from being forcibly disconnected to affect the communication quality despite the fact that a mobile station is communicating in a radio jurisdiction the mobile station has moved to.
As typical of the base station, capable of performing the above-described acceptance control, there is, for example, a base station described in Non-Patent Publication 1. This base station has the function of incessantly measuring the quantity of the uplink and the downlink transmission power for a user whose line connection request has been allowed by acceptance control to monitor whether or not the wireless section is congested with connected users. In case the wireless section is congested, the line connection requests from the user is refused, as a principle, except in case of an emergency, and processing e.g. of lowering the speed of communication stepwise is carried out, beginning from users exploiting high-speed services of packet communication.
Non-Patent Publication 1: 3 GPP (3rd Generation Partnership Project), Extended Abstract R3-030020, Target Architecture for UTRAN Evolution (Nokita), TSG-RAN Working Group 3 Rel6 Adhoc in Wokingham, Berkshire, UK, 17 Jan., 2003